International Science Index

International Journal of Mechanical and Mechatronics Engineering

An Analytical Model for Heat and Mass Transfer Processes in New Hybrid Indirect/Direct Evaporative Cooler Design with Parallel Flow Configuration
This study aims at evolving an analytical model for the coupled heat and mass transfer processes in new hybrid (indirect-direct) evaporative cooler design under different layouts and operating conditions with parallel flow configuration. Conventionally, evaporative cooler designs have been based on the concept of heat exchange between primary and secondary flows of parallel/ counterflow configuration. The objectives of the new design are introducing an effective small system dealing with the only primary flow without secondary flow at which the indirect and direct processes have existed in the same channel, and providing an appropriate alternative of mechanical vapor compression system for dry climate regions. The importance of such system is not limited to the energy-saving and environment safety, but it is extended to redeem the bacteria source, maintenance, and cleaning. In modeling, new mathematical equations have derived which conjugate the flow and channel wall temperature changing along together in the indirect section (dry section), and direct section (wet section). Diffusion mass transfer of water vapor and relative humidity variation within the channel have considered and calculated by analogy with the convection heat transfer equations; to increase the model accuracy, the value of Lewis factor was not considered as a unity. However, the effects of changing the operation conditions and channel wall thickness were considered during the calculations of the system's performance. Through the comparison, the results show that the hybrid design can be the future of the evaporative cooling system.
Optimum Design of Hybrid (Metal-Composite) Mechanical Power Transmission System under Uncertainty by Convex Modelling
The design models dealing with flawless composite structures are in abundance, where the mechanical properties of composite structures are assumed to be known a priori. However, if the worst case scenario is assumed, where material defects combined with processing anomalies in composite structures are expected, a different solution is attained. Furthermore, if the system being designed combines in series hybrid elements, individually affected by material constant variations, it implies that a different approach needs to be taken. In the body of literature, there is a compendium of research that investigates different modes of failure affecting hybrid metal-composite structures. It covers areas pertaining to the failure of the hybrid joints, structural deformation, transverse displacement, the suppression of vibration and noise. In the present study a system employing a combination of two or more hybrid power transmitting elements will be explored for the least favourable dynamic loads as well as weight minimization, subject to uncertain material properties. Elastic constants are assumed to be uncertain-but-bounded quantities varying slightly around their nominal values where the solution is determined using convex models of uncertainty. Convex analysis of the problem leads to the computation of the least favourable solution and ultimately to a robust design. This approach contrasts with a deterministic analysis where the average values of elastic constants are employed in the calculations, neglecting the variations in the material properties.
The Onset of Ironing during Casing Expansion
Shell has developed a novel mono-diameter well concept for oil and gas wells as opposed to the traditional telescopic well design. A Mono diameter well design allows well to have a single inner diameter from the surface all the way down to reservoir to increase production capacity, reduce material cost and reduce environmental footprint. This is achieved by expansion of liners (casing string) concerned using an expansion tool (e.g. a cone). Since the well is drilled in stages and liners are inserted to support the borehole, overlap sections between consecutive liners exist which should be expanded. At overlap, the previously inserted casing which can be expanded or unexpanded is called the host casing, and the newly inserted casing is called the expandable casing. When the cone enters the overlap section, an expandable casing is expanded against a host casing, a cured cement layer and formation. In overlap expansion, ironing or lengthening may appear instead of shortening in the expandable casing when the pressure exerted by the host casing, cured cement layer and formation exceeds a certain limit. This pressure is related to cement strength, thickness of cement layer, host casing material mechanical properties, host casing thickness, formation type and formation strength. Ironing can cause implications that hinder the deployment of the technology. Therefore, the understanding of ironing becomes essential. A physical model is built in-house to calculate expansion forces, stresses, strains and post expansion casing dimensions under different conditions. In this study, only free casing and overlap expansion of two casings are addressed while the cement and formation will be incorporated in future study. Since the axial strain can be predicted by the physical model, the onset of ironing can be confirmed. In addition, this model helps in understanding ironing and the parameters influencing it. Finally, the physical model is validated with Finite Element (FE) simulations and small scale experiments. The results of the study confirm that high pressure leads to ironing when the casing is expanded in tension mode.
Regulation, Co-Regulation and Self-Regulation of Civil Unmanned Aircrafts in Europe
Safety and security concerns play a key role during the design of civil UAs (aircraft controlled by a pilot who is not on-board it) by the producers and the offer of different services by the operators. At present, European countries have fragmented regulations about the manufacture and use of civil drones, therefore the European institutions are trying to approach all these regulations into a common one by 2019. In this sense, not only Law but also Ethics can give guidelines to the industry in order to obtain better reports from their clients. Moreover, the European Aviation Safety Agency (EASA), as an Agency of the European Union, promotes the highest common standards of safety and develops common safety rules at the European level. This Agency and their National equivalents monitor the activity of producers and operators, but depending on the size of the drone this activity could cover regulation measures or ethical recommendations. In this sense, the aim of our analysis is to categorize the concerns, measures and types of hard-soft regulations that we find in the European Union. Our study is based on a content analysis from three sources of information: academic papers, policies and regulation proposals from the European Union, and the regulation of some European countries. From a comparative analysis of the results, we evaluate the different concerns, regulations, and solutions of the National Laws and the European proposal. Taking into account the different regulation systems of the European members, we can find two groups of countries: countries regulation-centered, where legal regulation covers the majority of cases, and countries jurisprudence-centered, where co-regulation is enhanced. After this evaluation, and applying benchmarking, we can classify the best practices that could fit better with each type of regulation: legal regulation, co-regulation, and self-regulation. We show how technology is very difficult to regulate and, for this reason, other tools, such as co-regulation and self-regulation, although soft instruments are useful alternatives for the manufacturers and operators of civil drones. In general, few countries have taken self-regulation as a solution for some problems although in other industry sectors it has positive experiences. With these results, we would like to give advice to the European industry, as well as give new insights to the academia and policymakers.
Managing Uncertainty in the Unmanned Aircraft System Safety Performance Requirements Compliance Process
The Unmanned Aircraft System (UAS) industry is rapidly evolving the aviation sector. However, as with any new technology, there are associated safety risks. Till date, these risks have largely been managed through the imposition of significant restrictions on the operation of these systems, including prohibiting their flight over populated areas. It is now broadly recognised that airworthiness regulations should be tailored to the different UAS types and their Concepts of Operations, based on the level of risk posed. Consequently, UAS are likely to require certification against a prescriptive code of airworthiness requirements, which includes showing compliance to system safety regulations (Part 1309 regulations). The challenge, however, lies in applying the system safety process to UAS, which lack the data and operational heritage of conventionally piloted aircraft. The part of the system safety regulations that is of relevance to this research is the System Safety Performance Requirements (SSPR). The low data and high uncertainty associated with UAS make showing compliance to the SSPR a challenge. The current System Safety Assessment (SSA) process as used for conventional civil aviation systems does not address this uncertainty. A more comprehensive treatment of uncertainty is required for more rational, objective, and consistent compliance decision making. A fundamentally new approach to system safety, which aims to address these challenges, has already been proposed by the authors. It proposes a significant change to how aviation safety practitioners currently undertake regulatory compliance activities and is in line with contemporary decision making approaches first proposed by the nuclear industry (also suffers from low data and high risk and uncertainty). The objective of this paper is to provide a description of the overall SSPR framework and extend the existing approach by showing how uncertainties in the assignment of consequence severities to failure modes can be considered. The basic principles of Bayesian analysis, coupled with Bayesian inference techniques, Bayesian Belief Networks and normative decision making will be employed while developing the model. Some of the advantages of the new approach include, 1) providing a mathematically robust method for systematically combining subjective and objective data sources used in the SSA process (e.g., accident and incident reports and expert judgement); 2) providing a mathematically robust means for updating SSA as new technical or operational data is obtained; 3) supporting inductive and deductive reasoning in relation to the system safety of UAS (e.g., predictive assessments or incident analysis); 4) being compatible with existing system safety modelling and analysis tools (e.g., Functional Hazard Assessments (FHA)) 5) supporting more justifiable and systematic compliance findings; 6) facilitating compliance findings to be made on the basis of compliance risk; 7) reducing the need for conservative assumptions and the subsequent impost of unnecessary costs on the UAS industry. This paper describes a fundamentally new approach to system safety compliance, which can be applied to UAS (or other aviation systems, where there is high uncertainty). The approach is particularly suited to 'new aviation systems', where the state of knowledge and availability of data to support system safety assessments is evolving.
Autonomous Flight Control for Multirotor by Alternative Input Output State Linearization with Nested Saturations
Multirotor is one of the most popular types of small unmanned aircraft systems and has already been used in many areas including transport, military, surveillance, and leisure. Together with its popularity, the needs for proper flight control is growing because in most applications it is required to conduct its missions autonomously, which is in many aspects based on autonomous flight control. There have been many studies about the flight control for multirotor, but there is still room for enhancements in terms of performance and efficiency. This paper presents an autonomous flight control method for multirotor based on alternative input output linearization coupled with nested saturations. With alternative choice of the output of the multirotor flight control system, we can reduce computational cost regarding Lie algebra, and the linearized system can be stabilized with the introduction of nested saturations with real poles of our own design. Stabilization of internal dynamics is also based on the nested saturations and accompanies the determination of part of desired states. In particular, outer control loops involving state variables which originally are not included in the output of the flight control system is naturally rendered through this internal dynamics stabilization. We can also observe that desired tilting angles are determined by error dynamics from outer loops. Simulation results show that in any tracking situations multirotor stabilizes itself with small time constants, preceded by tuning process for control parameters with relatively low degree of complexity. Future study includes control of piecewise linear behavior of multirotor with actuator saturations, and the optimal determination of desired states while tracking multiple waypoints.
Infrastructure-Free Cooperative Relative Localization for Mobile Unmanned Aerial Vehicles
Relative positioning among multiple unmanned systems is essential for numerous applications, such as formation and rendezvous control. Instead of achieving the relative positions by calculating the difference of each global position, we consider the problem of distance-based cooperative relative localization for multiple unmanned aerial vehicles in the absence of global coordinates. For the flexible implementation purpose, there exist no infrastructures with known global or local position preset in the test site. All UAVs which are equipped with ultra-wideband modules are able to measure the relative distance and communicate between themselves and their neighbours. We propose a computing and filtering based collaborative approach for the purpose of relative localization and show that the estimate is stable under mild conditions. We also design an consensus based fusion approach which needs the information exchange among the UAVs to enhance their localization precision. Simulation and flight results show the effectiveness of the proposed approaches.
Mean Stress Sensitivity Factor: The Effect of Corrosive Environment
Corrosion fatigue failure is a fundamental design consideration in many industrial fields, particularly for mining industry, where pump components work under the influence of a corrosive environment in fatigue regimes. Nowadays, such components are usually made of low carbon steels because of its relatively low price and good material properties. However, this type of steel is subjected to the intensive corrosion influence. Furthermore, mean stress investigation is of high importance for the design since it can widely influence the fatigue strength. The effect of mean stress on fatigue life of circular cross section specimens made from low carbon steel is presented. Force controlled constant amplitude axial fatigue tests in the regime of 105 to 107 cycles were carried out for various stress ratio, R, under two different environment conditions: (i) without any corrosion, in air, (ii) in-situ corrosion fatigue under low salinity solution flow. Both sets of experimental data are used to calculate the mean stress sensitivity factor, in different condition of stress ratio, and number of cycles and two trends are compared to evaluate the effect of corrosion on this behavior. Main numerical models to predict the effect of mean stress are used to estimate the equivalent mean stress, and through these data, the mean stress sensitivity factor is estimated. Finally, a comparison between numerical results and experimental results is shown to assess the effectiveness of numerical model, both in neutral and corrosive environment. Experimental results show that the effect of fresh water environment is to reduce the fatigue strength of the material: the degradation is higher at lower level of stress but occurs even at lower number of cycles. Moreover, the mean stress sensitivity factor increases in corrosive environment, compared to results obtained in air. This trend suggests a severest effect of mean stress on corrosion fatigue. The present study aims to evaluate the degradation of fatigue strength caused by corrosive environment and further decrease due to mean stress effect.
An Experimental Investigation of Air Entrainment Due to Water Jets in Crossflows
Vertical water jets discharging into free surface turbulent cross flows result in the ingression of a large amount of air in the body of water and form a region of two-phase air-water flow with a considerable interfacial area. This research presents an experimental study of the two-phase bubbly flow using image processing technique. The air ingression and the trajectories of bubble swarms under different experimental conditions are evaluated. The rate of air entrainment and the bubble characteristics such as penetration depth, and dispersion pattern were found to be affected by the most influential parameters of water jet and cross flow including water jet-to-crossflow velocity ratio, water jet falling height, and cross flow depth. This research improves understanding of the underwater flow structure due to the water jet impingement in crossflow and advances the practical applications of water jets such as artificial aeration, circulation, and mixing where crossflow is present.
Automated Buffer Box Assembly Cell Concept for the Canadian Used Fuel Packing Plant
The Canadian Used Fuel Container (UFC) is a mid-size hemispherical headed copper coated steel container measuring 2.5 meters in length and 0.5 meters in diameter containing 48 used fuel bundles. The contained used fuel produces significant gamma radiation requiring automated assembly processes to complete the assembly. The design throughput of 2,500 used fuel containers per year places constraints on equipment and hot cell design for repeatability, speed of processing, robustness and recovery from upset conditions. After UFC assembly, the UFC is inserted into a Buffer Box (BB). The BB is made from adequately pre-shaped blocks (lower and upper block), made from Highly Compacted Bentonite (HCB) material. The blocks are practically ‘sandwiching’ the UFC between them after assembly. This paper identifies one possible approach for the BB automatic assembly cell and processes. Automation of the BB assembly will have a significant positive impact on nuclear safety, quality, productivity and reliability.
Analyzing the Effect of Design of Pipe in Shell and Tube Type Heat Exchanger by Measuring Its Heat Transfer Rate by Computation Fluid Dynamics and Thermal Approach
Shell and tube type heat exchangers are predominantly used in heat exchange between two fluids and other applications. This paper projects the optimal design of the pipe used in the heat exchanger in such a way to minimize the vibration occurring in the pipe. Paper also consists of the comparison of the different design of the pipe to get the maximize the heat transfer rate by converting laminar flow into the turbulent flow. By the updated design the vibration in the pipe due to the flow is also decreased. Computational Fluid Dynamics and Thermal Heat Transfer analysis are done to justifying the result. Currently, the straight pipe is used in the shell and tube type of heat exchanger where as per the paper the pipe consists of the curvature along with the pipe. Hence, the heat transfer area is also increased and result in the increasing in heat transfer rate. Curvature type design is useful to create turbulence and minimizing the vibration, also. The result will give the output comparison of the effect of laminar flow and the turbulent flow in the heat exchange mechanism, as well as, inverse effect of the boundary layer in heat exchanger is also justified.
Damage Assessment Based on Full-Polarimetric Decompositions in the 2017 Colombia Landslide
Synthetic Aperture Radar (SAR) is an effective tool for damage assessment induced by disasters due to its all-weather and night/day acquisition capability. In this paper, the 2017 Colombia landslide was observed using full-polarimetric ALOS/PALSAR-2 data. Polarimetric decompositions, including the Freeman-Durden decomposition and the Cloude decomposition, are utilized to analyze the scattering mechanisms changes before and after-landslide. These analyses are used to detect the damaged areas induced by the landslide. Experimental results validate the efficiency of the full polarimetric SAR data since the damaged areas can be well discriminated. Thus, we can conclude the proposed method using full polarimetric data has great potential for damage assessment of landslides.
Detection of Wildfire Burn Scars in Samcheok, South Korea, Using Sentinel-1 Data
Wildfire burn scars are invaluable information which can be utilized in estimation of financial or ecological damage by the fire and in planning of post-fire treatment activities. Previous studies have been mainly focused on the application of optic and thermal images for detection of burn scars, using the vegetation indices and thermal response of the fire, respectively. However, these images from passive sensors require certain imaging conditions such as low cloud cover and sufficient illumination to produce reliable detection results. The use of Synthetic Aperture Radar (SAR) could be an effective alternative for it being an active sensor, available all-weather, day or night with high spatial resolution. In this study, Sentinel-1B images were employed to detect the burn scars of a wildfire which occurred in coniferous forest of Samcheok, South Korea in May 2017. The proposed change detection method is composed of two stages: firstly coherence images from pre-fire and post-fire SAR images were processed with simple change detection techniques (differencing, rationing) to emphasize the fire-induced surface changes. Then thresholding algorithm was applied to the images for separation of burnt and unburnt classes. For these binarized images, separability between burnt and unburnt classes was measured to evaluate the performance of the change detection techniques. In addition, to assess the accuracy of the proposed method, vegetation index data was used as a reference and compared with the detected wildfire burn scars.
Rheological Evaluation of Various Indigenous Gums
In the present investigation, rheology of the three different natural gums has been evaluated experimentally using MCR 102 rheometer. Various samples based on the variation of the concentration of the solid gum powder have been prepared. Their non-Newtonian behavior has been observed by the consistency plots and viscosity variation plots with respect to different solid concentration. The viscosity-shear rate curves of gums are similar and the behavior is shear thinning. Gums are showing pseudoplastic behavior. The value of k and n are calculated by using various models. Results show that the Herschel–Bulkley rheological model is reliable to describe the relationship of shear stress as a function of shear rate. R² values are also calculated to support the choice of gum selection.
Numerical Study on Enhancement of Heat Transfer by Turbulence
This paper scrutinizes the influences of turbulence on heat transport rate, Nusselt number. The subject matter of this investigation also deals with the improvement of heat transfer efficiency of the swirl flow obtained by rotating a twisted tape in a circular pipe. The conditions to be fulfilled to observe the impact of Reynolds number and rotational speed of twisted tape are: a uniform temperature on the outer surface of the pipe, the magnitude of velocity of water varying from 0.1 m/s to 0.7 m/s in order to alter Reynolds number and a rotational speed of 200 rpm to 600 rpm. The gyration of twisted tape increase by 17%. It is also observed that heat transfer is exactly proportional to inlet gauge pressure and reciprocally proportional to increase of twist ratio.
Experimental Study of Flow Effects of Solid Particles’ Size and Quantity in Porous Media
Regenerative cooling technique, using fuel as coolant, could be used to cool the porous walls of the future hypersonic combustion ramjet chamber. However, at high temperature, the fuel is pyrolysed and generates coke particles inside the porous materials. This gradual coking activity reduces the material’s permeability and thus the efficiency of the cooling system. In order to understand the relationship between the particles’ size and quantity and the through-flow in porous material, an experimental test bench was developed. It is composed of an autoclave equipped with a stirrer which is used to mix the water and the micrometric particles. Nitrogen is used to pressurize the autoclave at a constant inlet pressure (Pin), leading the mixture flow into the permeation cell which contains a disc sample of the studied material. The flow of the representative mixture (water and particles) is monitored by a pressure transducer and a mass flowmeter at the inlet and at the outlet of the permeation cell. All the sensors are connected to a data acquisition card that helps recording the transient variations in the measurement during the experiments. The porous material is weighted before each experiment. After the experiment, the sample is dried in an oven at 120°C for 90 minutes and weighted again. The achieved data are used to calculate the change in the permeability of the porous material, the mass of infiltrated particles (Mi), the mass passing through the porous materials (Mp), the mass accumulated on the material’s surface (Ma) and the particles deposition thickness (e), with respect to time of each experiment. In this work, the test bench is used to study the transport of different particle size (35
Exergy Analysis of a Vapor Absorption Refrigeration System Using Carbon Dioxide as Refrigerant
Vapor absorption refrigeration systems can replace vapor compression systems in many applications as they can operate on a low-grade heat source and are environment-friendly. Widely used refrigerants such as CFCs and HFCs cause significant global warming. Natural refrigerants can be an alternative to them, among which carbon dioxide is promising for use in automotive air conditioning systems. Its inherent safety, ability to withstand high pressure and high heat transfer coefficient coupled with easy availability make it a likely choice for refrigerant. Various properties of the ionic liquid [bmim][PF₆], such as non-toxicity, stability over a wide temperature range and ability to dissolve gases like carbon dioxide, make it a suitable absorbent for a vapor absorption refrigeration system. In this paper, an absorption chiller consisting of a generator, condenser, evaporator and absorber was studied at an operating temperature of 70⁰C. A thermodynamic model was set up using the Peng-Robinson equations of state to predict the behavior of the refrigerant and absorbent pair at different points in the system. A MATLAB code was used to obtain the values of enthalpy and entropy at selected points in the system. The exergy destruction in each component and exergetic coefficient of performance (ECOP) of the system were calculated by performing an exergy analysis based on the second law of thermodynamics. Graphs were plotted between varying operating conditions and the ECOP obtained in each case. The effect of every component on the ECOP was examined. The exergetic coefficient of performance was found to be lesser than the coefficient of performance based on the first law of thermodynamics.
Process Modeling in an Aeronautics Context
Many innovative projects exist in the field of aeronautics, each addressing specific areas so to reduce weight, increase autonomy, reduction of CO2, etc. In many cases, such innovative developments are being carried out by very small enterprises (VSE’s) or small and medium sized-enterprises (SME’s). A good example concerns airships that are being studied as a real alternative to passenger and cargo transportation. Today, no international regulations propose a precise and sufficiently detailed framework for the development and certification of airships. The absence of such a regulatory framework requires a very close contact with regulatory instances. However, VSE’s/SME’s do not always have sufficient resources and internal knowledge to handle this complexity and to discuss these issues. This poses an additional challenge for those VSE’s/SME’s, in particular those that have system integration responsibilities and that must provide all the necessary evidence to demonstrate their ability to design, produce, and operate airships with the expected level of safety and reliability. The main objective of this research is to provide a methodological framework enabling VSE’s/SME’s with limited resources to organize the development of airships while taking into account the constraints of safety, cost, time and performance. This paper proposes to provide a contribution to this problematic by proposing a Model-Based Systems Engineering approach. Through a comprehensive process modeling approach applied to the development processes, the regulatory constraints, existing best practices, etc., a good image can be obtained as to the process landscape that may influence the development of airships. To this effect, not only the necessary regulatory information is taken on board, also other international standards and norms on systems engineering and project management are being modeled and taken into account. In a next step, the model can be used for analysis of the specific situation for given developments, derive critical paths for the development, identify eventual conflicting aspects between the norms, standards, and regulatory expectations, or also identify those areas where not enough information is available. Once critical paths are known, optimization approaches can be used and decision support techniques can be applied so to better support VSE’s/SME’s in their innovative developments. This paper reports on the adopted modeling approach, the retained modeling languages, and how they all fit together.
Experimental Investigation of Flat Plate Closed Loop Pulsating Heat Pipe
Electronic devices are shrinking in their form factor every passing day on the one hand, while their functionality is increasing, on the other hand. This has certainly increased heat dissipation due to more functions and also made the heat flux severe due to the shrinking sizes. In this scenario, the thermal management of the devices need mechanisms for diffusion of these high heat fluxes. These mechanisms are supposed to be competitive from the economic point of view as well. Pulsating heat pipes (PHPs) have promised to be effective heat spreaders (more or less like the conventional heat pipes). Also from the point of view of fabrication, PHPs are less intensive than their conventional counter-parts. Despite these advantages, there still exists shortage of data both experimental and analytical, to predict and design PHPs with certainty. In this study, a flat plate configuration closed loop PHP of aluminium alloy has been experimentally verified for its thermal performance. The PHP with 12 channels, each 2.2 mm deep x 2.0 mm wide, was tested with deionized water and methanol for a fill ratio of 70% by volume for various orientations staring from Evaporator below Condenser (90°) to near horizontal (7.5°) for its thermal performance for a single heat load of 50 W. The PHP performance as expected was best at the 90° orientation with very little deterioration up to 45°. An attempt has been made to ascertain/resolve the critical angle after which the PHP ceases to perform. The overall thermal resistances were estimated for each orientation. The results also indicate that at smaller angles of inclination (near horizontal) methanol performed better than water.
Characterization of Plunging Water Jets in Crossflows: Experimental and Numerical Studies
Plunging water jets discharging into turbulent crossflows are capable of providing efficient air water interfacial area, which is desirable for the process of mass transfer. Although several studies have been dedicated to the air entrainment by water jets impinging into stagnant water, very few studies have focused on the water jets in crossflows. This study investigates development of the two-phase flow as a result of the jet impingements into crossflows by means of image processing technique and CFD simulations. Investigations are also conducted on the oxygen transfer and a correlation is established between the aeration properties and the oxygenation capacity of water jets in crossflows. This study helps the optimal design and the effective operation of the industrial and the environmental equipment incorporating water jets in crossflows.
Effect of Cellular Water Transport on Deformation of Food Material during Drying
Drying is a food processing technique where simultaneous heat and mass transfer take place from surface to the center of the sample. Deformation of food materials during drying is a common physical phenomenon which affects the textural quality and taste of the dried product. Most of the plant-based food materials are porous and hygroscopic in nature that contains about 80-90% water in different cellular environments: intercellular environment and intracellular environment. Transport of this cellular water has a significant effect on material deformation during drying. However, understanding of the scale of deformation is very complex due to diverse nature and structural heterogeneity of food material. Knowledge about the effect of transport of cellular water on deformation of material during drying is crucial for increasing the energy efficiency and obtaining better quality dried foods. Therefore, the primary aim of this work is to investigate the effect of intracellular water transport on material deformation during drying. In this study, apple tissue was taken for the investigation. The experiment was carried out using 1H-NMR T2 relaxometry with a conventional dryer. The experimental results are consistent with the understanding that transport of intracellular water causes cellular shrinkage associated with the anisotropic deformation of whole apple tissue. Interestingly, it is found that the deformation of apple tissue takes place at different stages of drying rather than deforming at one time. Moreover, it is found that the penetration rate of heat energy together with the pressure gradient between intracellular and intercellular environments is the responsible force to rupture the cell membrane.
Product Architecture and Production Process of Battery Modules from Prismatic Lithium-Ion-Battery Cells
The electrification of the power train is a fundamental technical transition in the automotive industry and poses a major challenge for established car companies. Providing the traction energy, requiring an ever greater amount of space within the car and having a high share of value-add the lithium-ion battery is a central component of the electric power train and a completely new component to car manufacturers at the same time. Being relatively new to the automotive industry, the current design of the product architecture and production process (including manufacturing and assembling processes) of lithium-ion battery modules do not allow for an easy and cost-efficient disassembly or product design change. Yet these two requirements will increase in importance with rising sales volumes of electric cars in the near future and need to be addressed for the electric car to be competitive with conventional power train systems. This paper focuses on the current product architecture and production process of common automotive battery modules from prismatic lithium-ion battery cells to derive impacts for a remanufacturing concept. The information necessary for this purpose were gathered by literature research, patent inquiries, industry expert interviews and first-hand experiences of the authors. On the basis of these results, the underlying causes for the design´s lack of remanufacturability and flexibility with regards to product design changes are examined. In all, this paper gives an extensive and detailed overview of the state of the art of the product architecture and production process of lithium-ion battery modules from prismatic battery cells, identifies its deficiencies and derives improvement measures.
Analysis of Radial Pulse Using Nadi-Parikshan Yantra
Diagnosis according to Ayurveda is to find the root cause of a disease. Out of the eight different kinds of examinations, Nadi-Pariksha (pulse examination) is important. Nadi-Pariksha is done at the root of the thumb by examining the radial artery using three fingers. Ancient Ayurveda identifies the health status by observing the wrist pulses in terms of 'Vata', 'Pitta' and 'Kapha', collectively called as tridosha, as the basic elements of human body and in their combinations. Diagnosis by traditional pulse analysis – NadiPariksha - requires a long experience in pulse examination and a high level of skill. The interpretation tends to be subjective, depending on the expertise of the practitioner. Present work is part of the efforts carried out in making Nadi-Parikshan objective. Nadi Parikshan Yantra (three point pulse examination system) is developed in our laboratory by using three pressure sensors (one each for the Vata, Pitta and Kapha points on radial artery). The radial pulse data was collected of a large number of subjects. The radial pulse data collected is analyzed on the basis of relative amplitudes of the three point pulses as well as in frequency and time domains. The same subjects were examined by Ayurvedic physician (Nadi Vaidya) and the dominant Dosha - Vata, Pitta or Kapha - was identified. The results are discussed in details in the paper.
The Influence of Surface Roughness on the Flow Fields Generated by an Oscillating Cantilever
With the current trend of miniaturisation of electronic devices, piezoelectric fans have attracted increasing interest as an alternative means of forced convection over traditional rotary solutions. Whilst there exists an abundance of research on various piezo-actuated flapping fans in the literature, the geometries of these fans all consist of a smooth rectangular cross section with thicknesses typically of the order of 100 um. The focus of these studies is primarily on variables such as frequency, amplitude, and in some cases resonance mode. As a result, the induced flow dynamics are a direct consequence of the pressure differential at the fan tip as well as the pressure-driven ‘over the top’ vortices generated at the upper and lower edges of the fan. Rough surfaces such as golf ball dimples or vortex generators on an aircraft wing have proven to be beneficial by tripping the boundary layer and energising the adjacent air flow. This paper aims to examine the influence of surface roughness on the airflow generation of a flapping fan and determine whether the induced wake can be manipulated or enhanced by energising the airflow around the fan tip. Particle Image Velocimetry (PIV) is carried out on mechanically oscillated rigid fans with various surfaces consisting of pillars, perforations and cell-like grids derived from the wing topology of natural fliers. The results of this paper may be used to inform the design of piezoelectric fans and possibly aid in understanding the complex aerodynamics inherent in flapping wing flight.
Wear Resistance and Mechanical Performance of Ultra-High Molecular Weight Polyethylene Influenced by Temperature Change
Ultra-high molecular weight polyethylene (UHMWPE) is extensively used in industrial and biomedical fields. The slippery nature of UHMWPE makes this material suitable for surface bearing applications, however, the operational conditions limit the lubrication efficiency, inducing boundary and mixed lubrication in the tribological system. The lack of lubrication in a tribological system intensifies friction, contact stress and consequently, operating temperature. With temperature increase, the material’s mechanical properties are affected, and the lifespan of the component is reduced. The understanding of how mechanical properties and wear performance of UHMWPE change when the temperature is increased has not been clearly identified. The understanding of the wear and mechanical performance of UHMWPE at different temperature is important to predict and further improve the lifespan of these components. This study evaluates the effects of temperature variation in a range of 20 °C to 60 °C on the hardness and the wear resistance of UHMWPE. A reduction of the hardness and wear resistance was observed with the increase in temperature. The variation of the wear rate increased 94.8% when the temperature changed from 20 °C to 50 °C. Although hardness is regarded to be an indicator of the material wear resistance, this study found that wear resistance decreased more rapidly than hardness with the temperature increase, evidencing a low material stability of this component in a short temperature interval. The reduction of the hardness was reflected by the plastic deformation and abrasion intensity, resulting in a significant wear rate increase.
Influence of Counter-Face Roughness on the Friction of Bionic Microstructures
The problem of quick and easy reversible attachment has become of great importance in different fields of technology. For the reason, during the last decade, a new emerging field of adhesion science has been developed. Essentially inspired by some animals and insects, which during their natural evolution have developed fantastic biological attachment systems allowing them to adhere and run on walls and ceilings of uneven surfaces. Potential applications of engineering bio-inspired solutions include climbing robots, handling systems for wafers in nanofabrication facilities, and mobile sensor platforms, to name a few. However, despite the efforts provided to apply bio-inspired patterned adhesive-surfaces to the biomedical field, they are still in the early stages compared with their conventional uses in other industries mentioned above. In fact, there are some critical issues that still need to be addressed for the wide usage of the bio-inspired patterned surfaces as advanced biomedical platforms. For example, surface durability and long-term stability of surfaces with high adhesive capacity should be improved, but also the friction and adhesion capacities of these bio-inspired microstructures when contacting rough surfaces. One of the well-known prototypes for bio-inspired attachment systems is biomimetic wall-shaped hierarchical microstructure for gecko-like attachments. Although physical background of these attachment systems is widely understood, the influence of counter-face roughness and its relationship with the friction force generated when sliding against wall-shaped hierarchical microstructure have yet to be fully analyzed and understood. To elucidate the effect of the counter-face roughness on the friction of biomimetic wall-shaped hierarchical microstructure we have replicated the isotropic topography of 12 different surfaces using replicas made of the same epoxy material. The different counter-faces were fully characterized under 3D optical profilometer to measure roughness parameters. The friction forces generated by spatula-shaped microstructure in contact with the tested counter-faces were measured on a home-made tribometer and compared with the friction forces generated by the spatulae in contact with a smooth reference. It was found that classical roughness parameters, such as average roughness Ra and others, could not be utilized to explain topography-related variation in friction force. This has led us to the development of an integrated roughness parameter obtained by combining different parameters which are the mean asperity radius of curvature (R), the asperity density (η), the deviation of asperities high (σ) and the mean asperities angle (SDQ). This new integrated parameter is capable of explaining the variation of results of friction measurements. Based on the experimental results, we developed and validated an analytical model to predict the variation of the friction force as a function of roughness parameters of the counter-face and the applied normal load, as well.
Heat Transfer Performance of a Small Cold Plate with Uni-Directional Porous Copper for Cooling Power Electronics
A small cold plate with uni-directional porous copper is proposed for cooling power electronics such as an on-vehicle inverter with the heat generation of approximately 500 W/cm2. The uni-directional porous copper with the pore perpendicularly orienting the heat transfer surface is soldered to a grooved heat transfer surface. This structure enables the cooling liquid to evaporate in the pore of the porous copper and then the vapor to discharge through the grooves. In order to minimize the cold plate, a double flow channel concept is introduced for the design of the cold plate. The cold plate consists of a base plate, a spacer, and a vapor discharging plate, totally 12 mm in thickness. The base plate has multiple nozzles of 1.0 mm in diameter for the liquid supply and 4 slits of 2.0 mm in width for vapor discharging, and is attached onto the top surface of the porous copper plate of 20 mm in diameter and 5.0 mm in thickness. The pore size is 0.36 mm and the porosity is 36 %. The cooling liquid flows into the porous copper as an impinging jet flow from the multiple nozzles, and then the vapor, which is generated in the pore, is discharged through the grooves and the vapor slits outside the cold plate. A heated test section consists of the cold plate, which was explained above, and a heat transfer copper block with 6 cartridge heaters. The cross section of the heat transfer block is reduced in order to increase the heat flux. The top surface of the block is the grooved heat transfer surface of 10 mm in diameter at which the porous copper is soldered. The grooves are fabricated like latticework, and the width and depth are 1.0 mm and 0.5 mm, respectively. By embedding three thermocouples in the cylindrical part of the heat transfer block, the temperature of the heat transfer surface ant the heat flux are extrapolated in a steady state. In this experiment, the flow rate is 0.5 L/min and the flow velocity at each nozzle is 0.27 m/s. The liquid inlet temperature is 60 °C. The experimental results prove that, in a single-phase heat transfer regime, the heat transfer performance of the cold plate with the uni-directional porous copper is 2.1 times higher than that without the porous copper, though the pressure loss with the porous copper also becomes higher than that without the porous copper. As to the two-phase heat transfer regime, the critical heat flux increases by approximately 35% by introducing the uni-directional porous copper, compared with the CHF of the multiple impinging jet flow. In addition, we confirmed that these heat transfer data was much higher than that of the ordinary single impinging jet flow. These heat transfer data prove high potential of the cold plate with the uni-directional porous copper from the view point of not only the heat transfer performance but also energy saving.
Numerical Investigation of the Needle Opening Process in a High Pressure Gas Injector
Gas internal combustion engines are widely used as propulsion systems or in power plants to generate heat and electricity. While there are different types of injection methods including the manifold port fuel injection and the direct injection, the latter has more potential to increase the specific power by avoiding air displacement in the intake and to reduce combustion anomalies such as backfire or pre-ignition. During the opening process of the injector, multiple flow regimes occur: subsonic, transonic and supersonic. To cover the wide range of Mach numbers a compressible pressure-based solver is used. While the standard Pressure Implicit with Splitting of Operators (PISO) method is used for the coupling between velocity and pressure, a high-resolution non-oscillatory central scheme established by Kurganov and Tadmor calculates the convective fluxes. A blending function based on the local Mach- and CFL-number switches between the compressible and incompressible regimes of the developed model. As the considered operating points are well above the critical state of the used fluids, the ideal gas assumption is not valid anymore. For the real gas thermodynamics, the models based on the Soave-Redlich-Kwong equation of state were implemented. The caloric properties are corrected using a departure formalism, for the viscosity and the thermal conductivity the empirical correlation of Chung is used. For the injector geometry, the dimensions of a diesel injector were adapted. Simulations were performed using different nozzle and needle geometries and opening curves. It can be clearly seen that there is a significant influence of all three parameters.
A Comparative Study of Black Carbon Emission Characteristics from Marine Diesel Engines Using Light Absorption Method
Recognition of the needs about protecting environment throughout worldwide is widespread. In the shipping industry, International Maritime Organization (IMO) has been regulating pollutants emitted from ships by MARPOL 73/78. Recently, the Marine Environment Protection Committee (MEPC) of IMO, at its 68th session, approved the definition of Black Carbon (BC) specified by the following physical properties (light absorption, refractory, insolubility and morphology). The committee also agreed to the need for a protocol for any voluntary measurement studies to identify the most appropriate measurement methods. Filter Smoke Number (FSN) based on light absorption is categorized as one of the IMO relevant BC measurement methods. EUROMOT provided a FSN measurement data (measured by smoke meter) of 31 different engines (low, medium and high speed marine engines) of member companies at the 3rd International Council on Clean Transportation (ICCT) workshop on marine BC. From the comparison of FSN, the results indicated that BC emission from low speed marine diesel engines was ranged from 0.009 to 0.179 FSN and it from medium and high speed marine diesel engine was ranged 0.012 to 3.2 FSN. In consideration of measured the low FSN from low speed engine, an experimental study was conducted using both a low speed marine diesel engine (2 stroke, power of 7,400 kW at 129 rpm) and a high speed marine diesel engine (4 stroke, power of 403 kW at 1,800 rpm) under E3 test cycle. The results revealed that FSN was ranged from 0.01 to 0.16 and 1.09 to 1.35 for low and high speed engines, respectively. The measurement equipment (smoke meter) ranges from 0 to 10 FSN. Considering measurement range of it, FSN values from low speed engines are near the detection limit (0.002 FSN or ~0.02 mg/m3). From these results, it seems to be modulated the measurement range of the measurement equipment (smoke meter) for enhancing measurement accuracy of marine BC and evaluation on performance of BC abatement technologies.
Study of NOx Estimation of Hydrogen Enriched Compressed Natural Gas Engine under Wide Range of Operating Condition
The dependency on the fossil fuels can be minimized by using the hydrogen enriched compressed natural gas (HCNG) in the transportation vehicles. However, the NOx emissions of HCNG engines are significantly higher, and this turned to be its major drawback. Therefore, the study of NOx emission of HCNG engines is a very important area of research. In this context, the experiments have been performed at the different hydrogen percentage, ignition timing, air-fuel ratio, manifold-absolute pressure, load and engine speed. Afterwards, the simulation has been accomplished by the quasi-dimensional combustion model of HCNG engine. In order to investigate the NOx emission, the NO mechanism has been coupled to the quasi-dimensional combustion model of HCNG engine. The three NOx mechanism: the thermal NOx, prompt NOx and N2O mechanism have been used to predict NOx emission. For the validation purpose, NO curve has been transformed into NO packets based on the temperature difference of 100 K for the lean-burn and 60 K for stoichiometric condition. While, the width of the packet has been taken as the ratio of crank duration of the packet to the total burnt duration. The combustion chamber of the engine has been divided into three zones, with the zone equal to the product of summation of NO packets and space. In order to check the accuracy of the model, the percentage error of NOx emission has been evaluated, and it lies in the range of ±6% and ±10% for the lean-burn and stoichiometric conditions respectively. Finally, the percentage contribution of each NO formation has been evaluated.